Virtual font fallback to OFM for pTeX

[t-tk]

Hallo, Thank you for developing dvisvgm.

I have proposed an enhancement of feature of virtual font which designates CJK TFM/OFMs.
The previous one is discussed at
Virtual font fallback to Japanese tfm
和文vf の fallback を dviware で

I have written some tests to show my expectation:
t-tk/texlive-source@3e82714

It does not work and fails by segmentation fault even if the test is in the conventional fallback feature.

I hope the features will be supported by future dvisvgm.
Thanks.

---

(Extended feature, 2023-04-29)

The rule for virtual fonts (VF) fallback is extended:
If a VF has no entry of a codepoint and the first
MAPFONT designates an OFM for (u)pTeX, then we designate the
glyph (usually with a fullwidth metric) of the same codepoint
with the same metrics of the codepoint in the OFM.

[mgieseki]

Thank you for the information. Could you please provide all files required to perform the tests independently of the TeX Live sources? Currently, I can't reproduce the segmentation faults. dvisvgm just prints several warnings, e.g.

*** dvisvgm: test for upjf_full

pre-processing DVI file (format version 3)
WARNING: font file 'upjv-r.mf' not found
WARNING: font file 'upjv-g.mf' not found
WARNING: font file 'upjf-r.mf' not found
WARNING: font file 'upjf-g.mf' not found
WARNING: font file 'cmr10.pfb' not found
processing page 1
  graphic size: 219.455205pt x 212.999624pt (77.129683mm x 74.860806mm)
  WARNING: can't embed font 'upjv-g'
  WARNING: can't embed font 'cmr10'
  WARNING: can't embed font 'upjf-r'
  WARNING: can't embed font 'upjv-r'
  WARNING: can't embed font 'upjf-g'
  output written to upjf_full.svg
1 of 1 page converted in 0.523378 seconds

As a first step it would help to have all data available to test a single case that leads to a segfault.

[t-tk]

If the following lines are comment out by #, the segfault will be reproduced.
https://github.com/t-tk/texlive-source/blob/3e827146f98f7be2a41149f6a5d74084ff43dbf4/texk/dvisvgm/tests/dvisvgm-uptex.test#L36-L39

[mgieseki]

Ok, thanks for the hint. I've fixed the cause of the segfaults.

[mgieseki]

The latest changes add OFM support and the corresponding VF fallback mechanism.

[t-tk]

Thank you for the update.
I imported the sources and tested.
The segfault was fixed, but I could not get the same result between w/ and w/o fallback.

t-tk/texlive-source@aea9856

[mgieseki]

Do you get any warning messages from dvisvgm? For my tests I needed to adapt your upjf.map because it doesn't specify font files for the fonts listed there. Thus, I got the warnings shown above.

I use these entries taken from texk/dvipdfm-x/tests/upjf.map and get correct conversion results with them:

upjf-r   UniJIS-UTF16-H  HaranoAjiMincho-Regular.otf
upjf-g   UniJIS-UTF16-H  HaranoAjiGothic-Regular.otf
upjv-r   UniJIS-UTF16-V  HaranoAjiMincho-Regular.otf
upjv-g   UniJIS-UTF16-V  HaranoAjiGothic-Regular.otf

[t-tk]

Thank you for your comment.
I got intended results by using the following entries in the map file upjf.map.

t-tk/texlive-source@27ac1f7

upjf-r   unicode  HaranoAjiMincho-Regular.otf
upjf-g   unicode  HaranoAjiGothic-Regular.otf
upjv-r   unicode  HaranoAjiMincho-Regular.otf
upjv-g   unicode  HaranoAjiGothic-Regular.otf

[mgieseki]

Great, thanks for the confirmation. Since the additions seem to work as expected, I'm closing the ticket for now. Feel free to open it again if you still find any issues.

[t-tk]

Thank you for your support.